Process of liberating fatty acids in fatty material



Patented Dec. 29, 1936 PROCESS OF LIBERATING FATTY ACIDS IN FATTYMATERIAL Eddy W. Eckey, Wyoming, and Charles 0. Clark, St. Bernard,Ohio, assignors to The Procter & Gamble Company, Cincinnati, Ohio, atcorporation of Ohio No Drawing- Application October 2c 1933, Serial No.695,374.

16 Claims. (01'. 87-12) This invention relates to an improved processfor forming free fatty acids in a fatty material and, more particularly,in edible fats. It is a feature of the invention that the formation ofthe fatty acids is effected without injury to the color, flavor, orkeeping quality of the fat.

More specifically, the invention relates to an improved process forconverting soap which is mixed with fat to the corresponding free fattyacid.

The method commonly used heretofore of liberating the fatty acids fromsoap in fatty mixtures has comprised the incorporation in the mixture ofan aqueous solution of a mineral acid, usually at the boiling point ofthe solution, and thereafter to allow the mixture to settle until itseparates into an oily layer floating on an aqueous layer. This methodis detrimental, to the quality of the fat; troublesome emulsions form,especially in thecase of superglycerinated fat, 1. e. a fatty glyceridemixture containing monoand/or diglycerides; the color of the fat usuallydarkens, and the flavor, if the fat is of an edible grade, is injured sothat in many cases the product is rendered totally unsuitable for ediblepurposes. Furthermore, oxidation commonly occurs due to the unavoidableexposure of the fat to air for a considerable period at the hightemperature used in the process. These difiiculties are overcome by ourimproved procedure.

It has been recently recognized that the addition of free fatty acid toshortening fats is highly advantageous and thus a need has developed fora method by which free fatty acid may be con veniently and economicallyformed in such fats without injuring the color, flavor, or keepingquality of the fat. It has also been found that the incorporation ofcertain amounts of superglycerinated fat in shortening is highlyadvantageous and in the process of producing monoand diglycerides bytreatment of a triglyceride with additional glycerin in the presence ofa soap catalyst, it becomes desirable to decompose this soap catalyst toliberate the fatty acids contained therein. Our invention may be readilyemployed for this purpose, and the formation of emulsions in mixtureswhich ordinarily would form relatlvely stable emulsions is avoided.

It is a further feature of the invention that the salts formed asby-products of the reaction of the soap and acid can be separatedreadily and completely from the fatty material.

Any desired amount of free fatty acid can be formed in a shortening fatby first treating the fat with a sufilcient'quantity of caustic soda orother alkali to saponify a portion thereof, and by subsequentlydecomposing the soapthus formed with a suitable acid. It is an importantfeature of the present invention that the mixture of fat and soap istreated at a temperature well above 5 the melting point of the fat withan acid strong enough to decompose the soap, the acid being used inrather concentrated form and the conditions of temperature and moisturecontent being so controlled as to convert the salts formed into a 10substantially dry precipitate which can be readily separated byfiltration or otherwise from the resulting fatty mixture containing freefatty acids.

A suitable filter-aid greatly assists in filtration. 15 We usuallypractice our process under a vacuum as explained later. The mixture iscooled, but not too near the graining point, before removing from thevacuum vessel, to minimize oxidation when subsequently exposed to theatmosphere. 20 The acid used for decomposing the soap may, if theproduct is not required for edible purposes, be any acid which isharmless to the fat and strong enough to decompose the soap and form asalt insoluble in the fat such, for example, as 25 sulphuric,phosphoric, hydrochloric, tartaric, lactic acid, sulphur dioxide, andmany others. If, however, the product is intended for edible purposes weprefer to select such an acid as is known to have a favorable retardingeffect on the ran- 30 cidiflcation of the fat. Various acids havingantioxidant action on fats may be employed, particularly phosphoric acidand sulphuric acid. The minimum quantity of added acid is not less thanthe calculated chemical equivalent of 35 the soap to be decomposed. Thusto decompose one mol. of sodium soap in our process requires one mol. ofa monobasic acid such as hydrochloric acid, and preferably nosubstantial excess of such an acid is used. In the case of polybasicacids, 4 we have found that the optimum quantity, from the standpoint ofthe quality of the fat mixture obtained in our process, lies between and1 mol. of added acid to each mol. of fatty acid to be liberated, Asidefrom the possibility of retarding 45 rancidity of the fat, polybasicacids such as sulphuric and phosphoric acid are preferred over monobasicacids because the buffer action of their acid salts insures a wide rangein the quantity of acid which may be added without 50 danger of leavingin the finished product either undecomposed soap oran excess of the freemineral acid.

The concentration of the added acid is preferably between 50 per centand 85 per cent in aqueous solution. Other concentrations may be used,but when'stronger, the reaction is apt not to proceed smoothly orcompletely, and, if weaker, an undesired amount of water is therebyintroduced which may give difficulty in the subsequent filtration unlessremoved by longer heating than would otherwise be required.

The object of the filter-aid is to assist in filtering the salts formedand any other material such as glycerin, although in many cases theproduct can be filtered without any added filter-aid. Various filter-aidmaterials may be used, such as carbon, paper pulp, fullers earth,kieselguhr, and other materials having good filtering and absorbentproperties, but kieselguhr, preferably untreated except for drying andpulverizing, has been found to be especially satisfactory. The quantityrequired will vary but should be sufiicient to form with theprecipitated salts etc. a mass that can be readily filtered. In usingkieselguhr a weight varying from one half up to twice the weight of thesalt to be removed gives satisfactory results. When considerable freeglycerin is present, as in the reaction mixture obtained when makingsuperglycerinated fats, more filteraid is necessary than in thesubstantial absence of glycerin.

The mixture is agitated during the reaction period by any suitablemeans, such as a mechanical agitator or a stream of dry steam or otherinert gas.

We prefer to operate under reduced pressure although in some cases it isfeasible to operate without this condition; for example, if the moisturein the fatty soap mixture and in the added acid is suitably adjusted toyield a precipitated salt dry enough to filter readily with thefilteraid used, or if the mixture can be heated in an open vessel longenough to dry out any excess moisture present, and if exposure to airduring the reaction is not objectionable, the vacuum may be dispensedwith. On the other hand, if an edible product of high grade and goodkeeping quality is required, a vacuum is advantageous by preventingexposure to the atmosphere. Furthermore, if, as commonly occurs, enoughmoisture is present to interfere with the subsequent filtering of theprecipitated salts. the vacuum permits the excess moisture to evaporaterapidly even at relatively low temperatures. The degree of vacuumrequired is not critical, but should be high enough to accomplish theobjects stated. We prefer to use a vacuum of at least 25 inches ofmercury. It is necessary to have the salts and filter-aid substantiallydry when filtered, or otherwise separated in order to obtain a rapid andsatisfactory separation.

The best temperature for treatment will vary according to the nature ofthe fatty mixture, the acid used, and other conditions, but during theaddition of the acid it should usually lie between C. and 110 C. Itshould be well above the melting point of the fat to ensure a rapid andcomplete reaction, and also to evaporate any excess moisture andcoagulate the precipitated salts so that they can be readily filtered.

Precipitated salts and filter-aid are easily separated from the fat bypumping the mixture through an ordinary filter-press. Other methods,such as settling, centrifuging, or combinations of these methods may beused.

The filter cake, or the mass separated from the fat by centrifuging orother means, will unavoidably retain a certain amount of the fattymixture which, however, can be recovered by vari- I ous well knownmeans, such as extraction with a volatile solvent or by mixture withwater or dilute acids in which case the fatty matter will separate andfioat on top.

The following examples will show clearly how the invention may be putinto practice.

Example 1 A superglycerinated fat mixture consisting of the productobtained by reaction of partially hydrogenated cottonseed oil withglycerol in vacuum at 170 C. with soap as catalyst, in the proportionsof hydrogenated cottonseed oil, 100 parts, glycerol, 18.5 parts, sodiumsoap, 3.3 parts, is treated as follows.

Into a closed tank of 10,000 lbs. capacity, equipped with a mechanicalagitator and cooling coils, is put 100 lbs. of kieselguhr (celite F.C.). The opening is closed and a vacuum, preferably of at least 25inches, is drawn on the tank. Five thousand pounds of the hot reactionproduct described above (consisting of mono-, di, and triglycerides,together with soap and some free glycerol), is introduced. The agitatoris started and water turned into the cooling coils if necessary to coolthe mixture. When the temperature has dropped to 105 C., 43 lbs. ofortho-phosphoric acid, strength, is added. The agitation and cooling arecontinued for about 30 minutes or more when the temperature of the stockis reduced to 65 C., and the reaction is'completed. The cooling water isshut off, and the charge is pumpedfrom the acidulating vessel through afilter-press. Filtration is rapid, and a clear oil of good qualitycontaining free fatty acids but no soap is obtained. The cake left inthe press consists of kieselguhr mixed with sodium acid phosphates,glycerol, and some fatty matter.

Example 2 Into a round bottom 1 liter flask, fitted with an outlet fordrawing a vacuum, and with two inlet tubes, one leading to the bottom ofthe flask for providing steamagitation, and the other leading into theflask for addition of liquids, is placed 350 grams of the reactionproduct described in Example 1, together with '7 grams of kieselguhr. Avacuum of 25 inches is applied to the flask, and dry steam is introducedfor agitation. The charge is brought to a temperature of C. and then 5grams of a 50 per cent solution of sulphuric acid is added. Agitationwith dry steam is continued for 5 minutes, after which the reaction iscomplete, and the flask is then cooled rapidly to 65 C. The vacuum isthen broken, and the mixture filtered through paper on a suction filter.Filtration is rapid and a soapfree product is obtained, consisting ofglycerides and free fatty acids.

Example 3 Ninety-eight pounds of hydrogenated cottonseed oil oflard-like consistency and two lbs. (dry basis) of soda soap made eitherfrom the same or from any other fat or oil (or 100 lbs. of hydrogenatedcottonseed oil treated with 0.27 pound of caustic soda in such a way asto produce essentially the above mixture) are agitated at 100 C. underreduced pressure with 0.58 lb. of 85 per cent phosphoric acid. One totwo pounds of celite filter-aid may also be added, if desired, tofacilitate subsequent filtration, although not essential. Agitationunder reduced pressure is continued at 100 C. until the salts formed aresuitably coagulated and substantially dry. The mix-- ture is thenfiltered, yielding a clear, fatty mixture containing giycerides and freefatty acids. Filtration, while possible without the filter-aid, isgreatly facilitated by its use.

Example 4 Into around bottom 1 liter flask fltted with an outlet forvacuum and with two inlet tubes, one leading to the bottom of the flaskfor providing steam agitation and the other leading into the flask foraddition of liquids, is placed 350 grams of the reaction productdescribed in Example l. A vacuum of 25 inches is applied to the flaskand dry steam is introduced for agitation. The charge is brought to atemperature of 100 C. and 3 grams of 85 per cent phosphoric acid isadded. Agitation with dry steam is continued for 5 minutes, after whichthe reaction is complate, and the flask is then cooled rapidly and themixture filtered through paper with suction. Filtration proceeds moreslowly than when using a filter-aid, but the precipitated sodiumphosphates including the small amount of glycerin ordinarily present insuch mixtures as this can be removed by filtering through ordinaryfilter paper without filter-aid, if desired.

Example 5 One hundred parts of the reaction mixture described in Example1 are mixed with 4 parts oi an acid-activated bleaching earth by meansof a motor-driven agitator under a pressure of approximately 1 inch ofmercury. With the mixture at 100 C., 1 part of ortho-phosphoric acid,85% strength, is added and the agitation is continued for minutes. Themixture is cooled rapidly to 65 C. and filtered.

Example 6 A mixture of superglycerinated coconut oil with soap, made byreaction of 100 parts coconut oil with 25 parts glycerol in presence ofsoap equivalent to 0.45 part caustic soda is mixed with 2 parts ofdiatomaceous earth, and treated with phosphoric acid as in Example 5.

Certain variations from the conditions specifled in the illustrativeexamples are possible depending on the characteristics of the 'mixturefrom which the soap is to be removed and the use to which the product isto be put. By treating a few samples by the procedure described, it ispossible to determine in the case of any particular mixture theconditions of temperature and agitation required to obtain theprecipitated salt in a form which can readily be separated by filtrationor otherwise. We have found that, in general, higher temperatures andlonger times oi agitation give the best coagulation, although, if thetemperature at which the acid is added is too high, or if the agitationis continued too long, the coagulated materials tend to settle out as aheavy mud in the acldulation vessel. On the other hand, if the mixtureis agitated for too short a time or at too low a temperature, thecoagulation is insufllcient and slow filtration results. Between theselimits is a range of satisfactory operating conditions, as we havedescribed. The ranges of preferred conditions indifat, which comprisesadding the strong acid and an inert filter-aid to said mixture,agitating at a temperature at which the fat is fluid and suflicientlyhigh to evaporate excess moisture, until the soap is decomposed and theprecipitated salts and filter-aid are coagulated and dried enough tofilter, and separating the resulting coagulated salts and filter-aidfrom the fatty matter. 3 V

2. The process described in claim 1, in which the added acid is apolybasic acid having antioxidant action on fats, the amount of samebeing not less than one half'of one moi. and not substantially more thanone moi. per mol. of fatty acid liberated.

3. A process for increasing the free fatty acid content of fats whichcomprises mixing together at a temperature between 80 C. and 110 C.molten edible fat, soap, a filter-aid, and a concentrated aqueoussolution of an acid having anti-oxidant properties toward fats andselected from the group consisting of sulphuric and phosphoric acids,thereby liberating fatty acid dissolved in the fat and evaporating waterfrom the mixture so as to produce a substantially dry salt of the addedacid, and separating the resulting solid mass from the fatty matter.

4. The process described in claim 3, in which the concentration of addedacid lies between 50' per cent and 85 per cent anhydrous acid.

5. A process for liberating fatty acid by reaction of strong acid withsoap in mixture with fat containing monoglycerides and diglycerides offatty acids, which comprises adding the strong acid and an inertfilter-aid to said mixture, agitating the mixture at a temperature atwhich the fat is fluid until the soap is decomposed and the precipitatedsalts and filter-aid are coagulated and dried enough to filter, andsepartlng the resulting coagulated salts and filter-aid from the fattymatter.

6. The process described in claim 5, in which the precipitated salts aredried to a fllterableform by maintaining a pressure less thanatmospheric and a temperature high enough to evaporate moisture undersaid reduced pressure during a substantial part of the mixing period.

9. A process for liberating fatty acid by reaction of strong acid withsoap in mixture with fat, which comprises adding the strong acid to saidmixture, agitating at a temperature at which the fat is fluid until thesoap is decomposed and the precipitated salts are coagulated and driedenough to filter, and separating the resulting co-, agulated salts fromthe fatty matter.

10. The process described in claim 9, in which the added acid is a.polybasic acid having antioxidant action on fats, the amount of samebeing not less than one half of one mol. and not subst'antially morethan one moi. per moi. of fatty acid liberated.

11. A process for increasing the free fatty acid content of fats whichcomprises mixing together at a temperature between 80 C. and 110 C.molten edible fat, soap, and a concentrated aqueous solution of an acidhaving antioxidant properties toward fats and selected from the groupconsisting of sulphuric and phosphoric acids, thereby liberating fattyacid dissolved in the fat and evaporating water from the mixture so asto produce a substantially dry salt of the added acid, and separatingthe resulting solid mass from the fatty matter.

12. The process described in claim 11, in which the concentration ofadded acid lies between 50 per cent and 85 per cent anhydrous acid.

13. A process for liberating fatty acid by reaction of strong acid withsoap in mixture with fat containing monoglycerides and diglycerldes offatty acids, which comprises adding the strong acid, agitating themixture at a temperature at which the fat is fluid until the soap isdecomposed and the precipitatedsalts are coagulated and dried enough tofilter, and separating the resulting coagulated salts from the fattymatter.

14. The process described in claim 13, in which the acid used isphosphoric acid.

15. The process described in claim 9, in which 5 the precipitated saltsare dried to a fllterable form by maintaining a pressure less thanatmospheric and a temperature high enough to evaporate moisture undersaid reduced pressure during a substantial part of the mixing period.

16. The process described in claim 13, in which the precipitated saltsare dried to a fllterable form by maintaining a pressure less thanatmospheric and a temperature high enough to evaporate moisture undersaid reduced pressure durl5 ing a substantial part of the mixing period.EDDY W. ECKEY. CHARLES C. CLARK.

